Kernel Debugging Options

Glen Barber glen.j.barber at
Sat Jun 6 22:20:32 UTC 2009

On Sat, Jun 6, 2009 at 9:20 AM, Glen Barber<glen.j.barber at> wrote:
>> Hello everyone
>> I have a two-part question:
>> I have a minimally customized GENERIC kernel, with the only changes being:
>> options         KDB
>> options         KDB_UNATTENDED
>> options         DDB
>> and 'sysctl debug.debugger_on_panic' shows:
>> debug.debugger_on_panic: 0
>> However, after a panic loading the vboxdrv.ko module, the machine did
>> not reboot automatically after reboot.
> I meant "automatically after panic".  It's early, and I am apparently
> unable to type a coherent thought...
>> Here are my questions:
>> 1)  Would enabling DDB in the kernel prevent an automatic reboot after a panic?
>> 2)  Does the debugger wait for XX seconds of console inactivity before
>> rebooting?  I was under the impression from the handbook that the
>> machine would instantly reboot and after dumping the crash to vmcore0.
>>  Is this assumption incorrect?
>> Thanks in advance for any input.
> Also, if this is helpful, the userland / kernel are from two days ago, r193481:
> FreeBSD orion 7.2-STABLE FreeBSD 7.2-STABLE #0 r193481: Fri Jun  5
> 01:55:06 EDT 2009     root at orion:/usr/obj/usr/src/sys/ORION  i386

Sorry for the noise... Disabling DDB from the kernel corrected the
reboot issue.

Unless I am misunderstanding how it is worded, it is unclear from the
HTML docs that DDB overrides KDB_UNATTENDED.

If I am misunderstanding, I apologize, but I'm more curious if I am
experiencing unusual behavior with DDB enabled.

Glen Barber

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